The invention relates to the field of optical communication, and in particular to interleaver arrangements using more than one ring structures between two AWGs for aiding in crosstalk reduction and narrowing wavelength spacings.
Rapid growth of high-speed, broadband communication has led to a need to increase the capacity of optical communication networks. Wavelength division multiplexing (WDM) systems have key roles in meeting this need. Such networks require a variety of optical components to enable them to directly process light signals. Planar lightwave circuits (PLCs) fabricated using SiO2-based waveguides are being employed as an optical platform for various devices. Arrayed waveguide gratings (AWGs) are superior to other types of wavelength multiplexers/demultiplexers (MUX/DEMUX), such as dielectric multiplayer filters and fiber Bragg gratings in terms of compactness and large channel number. Thus, 16 to 64 channel AWGs have already been marketed and are widely used as MUX/DEMUX in WDM systems employed in communication networks.
Despite of the advantages of AWGs, one of the disadvantages is that in order to achieve WDM systems, there is a need to reduce crosstalks and thus to narrow the wavelength spacings between two channels especially for its application to analog signals. Since the principle of AWGs is constructive interference, the power distribution is always a sinusoidal function. This results in large crosstalks between two channels. The interleaver provides the ability to reduce crosstalk between two channels in AWGs so that wavelength spacings between two channels in the AWGs.
According to one aspect of the invention, there is provided a system for performing crosstalk in AWGs. The system includes a plurality of AWGs, wherein one of the AWGs receives an input signal. The AWGS are divided amongst a first selective group of the AWGs providing even-numbered channel outputs associated with an even-numbered selection of the input signal, and a second selective group of the AWGs providing odd-numbered channel outputs associated with an odd-numbered selection of the input signal. An interleaver arrangement includes a plurality of ring structures so as to provide appropriate filtering characteristics for the even-numbered channel outputs and odd-numbered channel outputs.
According to another aspect of the invention, there is provided a method of performing crosstalk in AWGs. The method includes providing a plurality of AWGs, wherein one of said AWGs receives an input signal. The AWGS are divided amongst a first selective group of said AWGs providing even-numbered channel outputs associated with an even-numbered selection of said input signal, and a second selective group of said AWGs providing odd-numbered channel outputs associated with an odd-numbered selection of said input signal. The method also includes providing an interleaver arrangement that includes a plurality of ring structures so as to provide appropriate filtering characteristics for said even-numbered channel outputs and odd-numbered channel outputs.